A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, five major sections, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is positioned at the front, or “inlet” section of the engine, and includes a fan that induces air from the surrounding environment into the engine, and accelerates a fraction of this air toward the compressor section. The remaining fraction of air induced into the fan section is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section raises the pressure of the air it receives from the fan section to a relatively high level. In a multi-spool engine, the compressor section may include two or more compressors, such as, for example, a high pressure compressor and a low pressure compressor. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel into a plenum formed by liner walls and a dome. The injected fuel is ignited in the combustor, which significantly increases the energy of the compressed air. The high-energy compressed air from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and generate energy. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass plenum.
In some engines, the compressor section is implemented with a centrifugal compressor. A centrifugal compressor typically includes at least one impeller that is rotationally mounted to a rotor and surrounded by a shroud. When the impeller rotates, it compresses the air received from the fan section and the shroud directs the air radially outward into a diffuser. The diffuser decreases the velocity and increases the static pressure of the air and directs the air into a deswirl assembly, which straightens the flow of the air before it enters the combustor section. The combustor section in some engines is implemented with an axial through-flow combustor that includes an annular combustor disposed within a combustor housing that defines a plenum. The straightened air enters the plenum and travels axially through the annular combustor where it is mixed with fuel and ignited.
Aerodynamic coupling of the components in a gas turbine engine affects engine performance, operability and efficiency. To achieve optimal performance for a system including a centrifugal compressor, the discharge flow from the centrifugal compressor is preferably suitably conditioned, the compressor discharge flow has minimal losses as it enters the combustor plenum, and maximum static pressure recovery is preferably achieved at the dome and liner walls of the combustor. Additionally, because the flow changes direction from radial to axial and transitions from a larger to a smaller radial area as it enters the turbine, the flow is preferably conditioned to a low mach number for combustor and system performance. However, when an axial through-flow combustor is used in conjunction with the centrifugal compressor, misalignment between the compressor discharge and turbine inlet may undesirably occur, which may pose challenges to satisfying performance requirements.
Hence, there is a need for efficient methods to aerodynamically couple a centrifugal compressor and an axial through-flow combustor which suitably directs and conditions the air flow for optimal performance.